modbus_send_rtu while(spin_lock); causing infinite loop.

[andrewmarles]

I found an issue where modbus_send_rtu would get stuck on waiting for the spin lock when it was called in the context of

core/modbus_rtu.c

Line 223 in 1445a42

packet->callbacks.on_rx_exception(ModBus_CRCError, packet->msg.context);

This seemed to be related to having two sources calling modbus_send in rapid succession (Modbus RGB plugin and VFD plugin). I was able to work around it by releasing the spinlock around the callback, but I'm not sure this is the best solution:

spin_lock = false;
packet->callbacks.on_rx_exception(ModBus_CRCError, packet->msg.context);
spin_lock = true;

I have also put the same unlock around the rx_timeout callback.

[terjeio]

Moving the spinlock is better? Or just removing it since queueing blocking calls is not possible?

    if((block &= !sys.blocking_event)) {

        if(is_blocking)
            return false;

        while(spin_lock);